1. Field of the Invention
This invention relates to jaw extenders to extend the throat (i.e., the distance between the working surfaces of opposing jaw faces) of machinist vises to permit machining of larger workpieces that could not otherwise be held in the normal vise-jaws.
2. Description of the Related Art
It has long been recognized by those who use vises having a stationary jaw and a movable jaw to hold workpieces for performing work thereon that many workpieces are either too large or of an irregular shape such that the standard jaws of the vise are inadequate to support the workpiece. As a result, jaw keys have been provided to increase the workpiece holding capacity of the vise. Examples of vises having jaw keys are found in U.S. Pat. Nos. 800,685; 2,741,145; 3,006,226; 4,078,782 and 4,422,629.
In addition to those patents directed to extending the clamping width of vise jaws, there are a number of patents directed to auxiliary jaws for special purposes. Patents of this type include U.S. Pat. Nos. 2,876,667 and 3,184,228.
Alternative devices to expanding the width of vise jaws include configuring the machining work surface to accept specially adapted clamps for holding the workpiece in position such as disclosed in U.S. Pat. No. 744,559 and a support device that provides adaptable clamping means, such as U.S. Pat. No. 4,306,709, wherein the clamping members are rotatable on the upper surface of the jaw and each end of the jaw assembly of the movable jaw is controlled by a separate threaded screw.
Although this diverse range of solutions to providing alternative jaw facings addresses problems faced by machinists, the solutions generally address but a single problem. For example, U.S. Pat. Nos. 4,078,782 and 4,422,629 disclose devices for extending the clamping width of the vise jaws but do not address the problem of maintaining the accuracy of the jaw extensions relative to a vise datum surface or extending the lateral width of the jaw faces while maintaining matched clamping surfaces. Further, the area of contact between the vise jaw extenders and the workpiece in the '782 and '629 patents is extensive thereby limiting continuous machining operations.